1. Field of the Invention
This invention pertains to a nozzle system for improving the thrust augmentation of a lift or propulsion device. It can optimally be used to improve the mixing with a secondary coflowing air stream.
2. Description of the Prior Art
According to the laws of momentum and energy conservation, improved lift or thrust can be obtained by accelerating a large mass of air to a low velocity. A well-known example of this principle is in the jet engines that propel the transport aircraft used by airlines. Almost all airlines use what is known as a fan jet or a forward fan engine. This essentially uses a multivane shrouded propeller external to the turbojet engine but powered by the turbojet engine. This device accelerates a large mass of air to a low velocity and therefore enhances the engine thrust. In an application of the present invention, a large mass of air is entrained through a diffuser by vortex rich air mixing with the secondary coflowing stream. The vortex rich air results from the unique nozzle configuration.
A nozzle structure is described in U.S. Pat. No. 4,311,291 to Gilbertson, et. al. that contains notches along the rear edge of the nozzle configuration. This has the effect of widening the jet stream while directing the jet stream rearwardly. The advantage of this type of nozzle structure would be found in a blown flap system. A flap increases lift by increasing the local velocity on the upper surface of a flap. This type of system is usually used in short take off and landing (STOL) aircraft. This type of system is not addressed in the present invention.
Typer, et. al. in U.S. Pat. No. 3,027,713 uses a slotted nozzle for noise suppression. This type of slotted nozzle reduces the engine noise at the expense of reducing the thrust.
A lobe mixer for gas turbine engines is described by Wynosky, et. al. in U.S. Pat. No. 4,149,375 to both suppress the noise and minimize the thrust loss. This is accomplished by mixing the fan flow stream with the engine flow stream by scalloping the side walls of the mixer which produces vortex sheets. This apparently enhances the mixing which minimizes the thrust loss and simultaneously suppresses the noise.
Papworth in U.S. Pat. No. 4,015,613 uses a nozzle shaped as a bowtie for cleaning tanks. This is completely unrelated art.
Kentfield, et. al. discloses a jet engine exhaust nozzle for VTOL aircraft in U.S. Pat. No. 3,428,257 where the turbulence of the exhaust gases passing through said nozzle is minimized by use of a bowtie shaped structure internal to the nozzle.
Lehman in U.S. Pat. No. 3,258,916 describes a means for vehicular steering using jet propulsion principles. In one of his embodiments, he changes a jet stream from an oval into a cross slot outlet. However, there is no mention of vortices.